Chapter 4 Cells and Tissues

Body Tissues  Cells are specialized for particular functions  Tissues  Groups of cells with similar structure and function  Four primary types  Epithelium  Connective tissue  Nervous tissue  Muscle

Epithelial Tissues  Found in different areas  Body coverings  Body linings  Glandular tissue  Functions  Protection  Absorption  Filtration  Secretion

Epithelium Characteristics  Cells fit closely together  Polarity: Tissue layer always has one free surface  Apical surface  Basal Surface  The lower surface is bound by a basement membrane (basal lamina)  Avascular (have no blood supply)  Innervated- supplied by nerve fibers  Regenerate easily if well nourished

Classification of Epithelium  Number of cell layers  Simple – one layer  Stratified – more than one layer

Classification of Epithelium  Shape of cells  Squamous – flattened  Cuboidal – cube-shaped  Columnar – column-like

Simple Epithelium  Simple squamous  Single layer of flat cells  Usually forms membranes  Mesothelium: Lines body cavities  Endothelium: Lines lungs and capillaries

Simple Epithelium  Simple cuboidal  Single layer of cube-like cells  Common in glands and their ducts  Forms walls of kidney tubules  Covers the ovaries

Simple Epithelium  Simple columnar  Single layer of tall cells  Often includes goblet cells, which produce mucus  Lines digestive tract

Simple Epithelium  Pseudostratified  Single layer, but some cells are shorter than others  Often looks like a double cell layer  Sometimes ciliated, such as in the respiratory tract  May function in absorption or secretion

Stratified Epithelium  Stratified squamous  Cells at the free edge are flattened  Found as a protective covering where friction is common  Locations  Skin  Mouth  Esophagus

Stratified Epithelium  Stratified cuboidal  Two layers of cuboidal cells  Stratified columnar  Surface cells are columnar, cells underneath vary in size and shape  Stratified cuboidal and columnar  Rare in human body  Found mainly in ducts of large glands

Stratified Epithelium  Transitional epithelium  Shape of cells depends upon the amount of stretching  Lines organs of the urinary system

Glandular Epithelium  Gland – one or more cells that secretes a particular product  Two major gland types  Endocrine gland  Ductless  Secrete hormones  Ex: pituitary gland, thyroid gland  Exocrine gland  Empty through ducts to the epithelial surface  Include sweat and oil glands

Forensic Anthropologists Analyze human remains and for this reason are important to different types of forensic investigations. Forensic anthropologists are called on after mass disasters such as earthquakes and tsunamis in order to assist in identifying human remains. They are also used at crime scenes to help recover evidence.

Connective Tissue  Found everywhere in the body  Includes the most abundant and widely distributed tissues  Functions  Binds body tissues together  Supports the body  Provides protection  For blood, provides transportation for substance

Connective Tissue Characteristics  Common origin (mesenchyme)  Variations in blood supply  Some tissue types are well vascularized  Some have poor blood supply or are avascular  Extracellular matrix  Non-living material that surrounds living cells

Structural Elements 1. Ground substance 2. Fibers Collagen Collagen Elastic Elastic Reticular Reticular 3. Cells Fibroblast Fibroblast Chondroblast Chondroblast Osteoblast Osteoblast hemocytoblast hemocytoblast

Classes of Connective Tissue 1. Connective tissue proper 2. Cartilage 3. Osseous (bone) 4. Blood

Connective Tissue Types  Dense connective tissue  Main matrix element is collagen fibers  Cells are fibroblasts  Examples  Tendon – attach muscle to bone  Ligaments – attach bone to bone

Connective Tissue Types  Areolar connective tissue  Most widely distributed connective tissue  Soft, pliable tissue  Contains all fiber types  Can soak up excess fluid

Connective Tissue Types  Adipose tissue  Matrix is an areolar tissue in which fat globules predominate  Many cells contain large lipid deposits  Functions  Insulates the body  Protects some organs  Serves as a site of fuel storage

Connective Tissue Types  Reticular connective tissue  Delicate network of interwoven fibers  Forms stroma (internal supporting network) of lymphoid organs  Lymph nodes  Spleen  Bone marrow

Connective Tissue Types  Hyaline cartilage  Most common cartilage  Composed of:  Abundant collagen fibers  Rubbery matrix  Entire fetal skeleton is hyaline cartilage

Connective Tissue Types  Elastic cartilage  Provides elasticity  Example: supports the external ear

Connective Tissue Types  Fibrocartilage  Highly compressible  Example: forms cushion-like discs between vertebrae

Connective Tissue Types  Bone (osseous tissue)  Composed of:  Bone cells in lacunae (cavities)  Hard matrix of calcium salts  Large numbers of collagen fibers  Used to protect and support the body

Connective Tissue Types  Blood  Blood cells surrounded by fluid matrix  Fibers are visible during clotting  Functions as the transport vehicle for materials

Nervous Tissue  Neurons and nerve support cells (neuroglial cells)  Function is to send impulses to other areas of the body  Irritability  Conductivity

Muscle Tissue  Function is to produce movement  Three types  Skeletal muscle  Cardiac muscle  Smooth muscle

Muscle Tissue Types  Skeletal muscle  Can be controlled voluntarily  Cells attach to connective tissue  Cells are striated  Cells have more than one nucleus

Muscle Tissue Types  Cardiac muscle  Found only in the heart  Function is to pump blood (involuntary)  Cells attached to other cardiac muscle cells at intercalated disks  Cells are striated  One nucleus per cell

Muscle Tissue Types  Smooth muscle  Involuntary muscle  Surrounds hollow organs  Attached to other smooth muscle cells  No visible striations  One nucleus per cell

Tissue Repair  Regeneration  Replacement of destroyed tissue by the same kind of cells  Fibrosis  Repair by dense fibrous connective tissue (scar tissue)  Determination of method  Type of tissue damaged  Severity of the injury

Events in Tissue Repair * add to notes * 1. Capillaries become very permeable  Introduce clotting proteins  Wall off injured area 2. Formation of granulation tissue 3. Regeneration of surface epithelium

Regeneration of Tissues * Add to notes *  Tissues that regenerate easily  Epithelial tissue  Fibrous connective tissue and bone  Tissues that regenerate poorly  Skeletal muscle  Tissues that are replaced largely with scar tissue  Cardiac muscle  Nervous tissue within the brain and spinal cord

Developmental Aspects of Tissue  Epithelial tissue arises from all three primary germ layers  Muscle and connective tissue arise from the mesoderm  Nervous tissue arises from the ectoderm  With old age there is a decrease in mass and viabililty in most tissues